Not Applicable.
This invention relates generally to waterproofing membranes and, more particularly, to an improved waterproofing membrane employing a waterproof film on which a bitumen adhesive is supported, and to a method of manufacturing such membranes.
In the construction industry, it is known to provide waterproofing membranes of various constructions which can be adhered to the walls, floors, decks, etc. of a building to seal them against the passage of water and moisture therethrough. A typical waterproofing membrane comprises a layer of waterproof elastomeric or synthetic resin material or composition that is applied to a bitumen adhesive, e.g. of modified asphalt or the like, and may include additional layers to strengthen or support the various layers of the membrane during manufacture and use. As with any product, waterproofing membranes must perform their intended waterproofing function at the lowest possible cost, be easy to manufacture and use, and permit application to a multitude of different types of construction surfaces and to conform to varying substrate shapes.
A problem that arises in the use of conventional waterproofing membranes, especially in underground applications, is hydrolysis. Hydrolysis is a process whereby prolonged exposure of the waterproof material to moisture, typically standing water, leads to a deterioration of the membrane""s ability to prevent the transmission of water. In an attempt to overcome the problems associated with hydrolysis, at least one known conventional membrane includes a waterproof layer incorporating high density polyethylene which is not vulnerable to hydrolysis. However, polyethylene possesses a relatively low transition temperature, above which both its dimensional stability and its ability to support a continuous load is lost relative to the dimensional stability and ability of the material to support a continuous load at room temperature.
Because this transition temperature of the material used in the waterproof layer is lower than the temperature at which the bitumen adhesive is capable of being extruded during manufacture, it is necessary to first extrude the adhesive onto a separate substrate, such as a release liner, allow the adhesive (asphalt) to cool to a temperature lower than the transition temperature of the waterproof layer, and subsequently apply the waterproof layer to the adhesive. The release liner is thus used as a substrate during the manufacturing process because it can support the weight of the adhesive at the coating temperature. Although it is possible to employ a waterproof layer that incorporates stabilizers or fillers such as glass fiber, mineral particles or the like to improve the mechanical properties of the material above its transition temperature, such compositions increase the cost of the membrane.
Several problems arise from the use of conventional membrane materials and methods of manufacture. For example, because the adhesive in the membrane must be allowed to cool before the waterproof layer can be applied during manufacture, large flat bed cooling devices are used, which consume a significant amount of space and provide only relatively slow convection cooling of the asphalt. As such, the manufacturing process is slow and expensive.
Other attempts to apply bitumen adhesive at high temperatures to a waterproofing film have been similarly unsuccessful. For example, attempts have been made to use roll coating techniques to apply bitumen to a waterproofing film. The bitumen is applied to a pair of rotating rolls on either side of the film, and subsequently transferred to the base sheet at the desired thickness. In these techniques, the rolls are internally cooled by circulating water so that the molten bitumen is cooled significantly before being applied to the film. Another techniques involving supporting the waterproofing film on a water-cooled conveyor belt has been considered, but has not proven effective. These methods involve additional process steps, equipment, and maintenance time. Ultimately, these methods are inefficient and result in a high cost conversion to produce the waterproofing membrane.
It is an object of the present invention to provide a waterproofing membrane that can be used to waterproof a wall, floor, deck or the like, and that will not deteriorate substantially with time due to hydrolysis.
It is another object of the invention to provide a method of manufacturing the waterproofing membrane that reduces the total cost and time of manufacture of the membrane.
In accordance with these and other objects of the invention, a waterproofing membrane is provided which includes, possibly among other features, a waterproof synthetic resin film presenting opposed first and second surfaces, and a bitumen adhesive supported on the first surface of the film. The adhesive possesses a coating temperature at which the adhesive can be coated on the film as a viscous liquid, and the synthetic resin film possesses a transition temperature above which the dimensional stability of the film and the ability of the film to support a continuous load is substantially reduced, e.g. by at least 50% relative to the dimensional stability and ability of the film to support a continuous load at room temperature. The transition temperature of the film is higher than the coating temperature of the adhesive, permitting the film to be used as a substrate for the adhesive during manufacture.
By providing a construction in accordance with the present invention, numerous advantages are realized. For example, by employing a waterproof film of the type employed in the invention, it is possible to manufacture the membrane using a method comprising the steps of raising the temperature of a bitumen adhesive to a coating temperature, and coating at least one surface of a web of waterproof synthetic resin film with the adhesive. Thereafter, the coated web can be cooled by running it over one or more chilled rollers that employ conduction to cool the membrane to a temperature at which it can be rolled up for storage or shipment to a work site. Thus, the method is much faster than conventional methods, and cooling of the membrane can be done more efficiently, resulting in a lower cost membrane.
In accordance with one aspect of the invention, the membrane includes a pair of adhesive layers, each of which is applied to an opposing surface of the synthetic resin film. By providing this construction, added protection is afforded the film against exposure to moisture, improving the durability of the membrane and reducing the effects of hydrolysis. As such, it is possible to employ synthetic resin materials in the film that do not, by themselves, exhibit excellent resistance to the effects of hydrolysis.
In accordance with another aspect of the invention, the membrane includes, among other features, a waterproof synthetic resin film having a thickness of less than about 3 mils, wherein the bitumen adhesive supported on a first surface of the film presenting laterally spaced side edges that are substantially coextensive with the side edges of the film. As such, the membrane is capable of being wrapped around corners and over other odd shaped walls and floors, and adheres well to many different types of surfaces.